Key Concepts of Section 19.1

Key Concepts of Section 19.1

Overview of the Cell Cycle and Its Control

  • The eukaryotic cell cycle is divided into four phases: G1 (the period between mitosis and the initiation of nuclear DNA replication), S (the period of nuclear DNA replication), G2 (the period between the completion of nuclear DNA replication and mitosis), and M (mitosis).

  • Cells commit to a new cell division at a specific point in G1 known as START or the restriction point.

  • Cyclin-CDK complexes, composed of a regulatory cyclin subunit and a catalytic cyclin-dependent kinase (CDK) subunit, drive the progression of a cell through the cell cycle.

  • Cyclins activate CDKs and are present only in the cell cycle stage that they promote.

  • CDK activities oscillate during the cell cycle. Positive and negative feedback loops drive these oscillations.

  • Surveillance mechanisms, called checkpoint pathways, guarantee that each cell cycle step is completed correctly before the next one is initiated.